Many systems are known in the prior art for cooking meats and other foods outdoors. Among devices of this type are covered cookers or closed barbecue pits, often referred to as "smokers". Closed cookers generally use combustible fuel in the form of wood charcoal. Holes in the bottom of the unit admit air for supporting the combustion and a damper at the top of the device controls release of the heated air and smoke. The food cooks in the hot gases and smoke, free of open flame. Because there is no flame, the cooking temperatures are much lower than those found with respect to open flame barbecues; consequently, covered cookers or closed barbecues can be left unattended for long periods of time.
Closed barbecues are commonly constructed of metal and are the modern equivalent of the barbecue pits long employed in the southern portion of the United States in which an open fire has been made in a pit lined with stone. After the fire heated the stones, the meat was wrapped, placed on the stones, and the pit was covered to prevent any combustion of the meat or wrapper from occurring.
While modern metal enclosed cookers are highly convenient and the food bears more than a passing resemblance to southern barbecue pit cooked food, the present day devices do have drawbacks.
Perhaps the greatest drawback of all is that closed cookers can and often do produce harmful carbon monoxide gas which contacts the food being cooked for prolonged periods of time. Of course, carbon monoxide gas is also produced by open barbecue cookers but the gas is readily dissipated or converted in such an arrangement because of direct exposure to the air. The essence of closed cookers is, however, the fact that they are substantially closed to the outside atmosphere, admitting air only through the bottom of the cooker.
Prior art closed cookers are also relatively thermally inefficient, at least partially due to the fact that calories are lost during the conversion of carbon dioxide first formed by the burning of the fuel to carbon monoxide.
Applicant is aware of the following United States Patents, which are believed to be representative of the current state of the barbecue cooker art, including the closed cooker art: U.S. Pat. Nos. 5,144,939, issued Sep. 8, 1992, 5,086,752, issued Feb. 11, 1992, 4,604,986, issued Aug. 12, 1986, 4,471,751, issued Sep. 18, 1984, 4,706,643, issued Nov. 17, 1987, 4,532,911, issued Aug. 6, 1985, 4,489,706, issued Dec. 25, 1984, 4,094,295, issued Jun. 13, 1978, 4,026,265, issued May 31, 1977, 3,974,760, issued Aug. 17, 1976, and 3,354,848, issued Nov. 28, 1967.